This invention relates generally to the field of human body protection during accidental impact with relatively rigid and massive structures and more particularly to an energy absorbing crush apparatus to constantly reduce the magnitude of acceleration (deceleration) suffered by a human body, or a trauma vulnerable portion thereof, during a crash event.
Although the invention finds particularly advantageous utilization in airline passenger, head impact protection applications and although, in the cause of clarity and brevity, much of the discussion below and presentation of examples relates specifically thereto, it is to be understood that the advantages of the invention are equally well manifest in other applications and configurations. For example, the principles described herein are useful in the protection of automobile, train, light airplane, and even cycle passengers from not only frontal head injury, but from frontal, side, or rear impact to such vulnerable body components as spine, torso, and pelvis.
An element of special concern in airplane crash scenarios is protecting the head so that catastrophic brain injury doesn't effectively or actually destroy a life in an otherwise survivable event. The most likely such scenario is a frontal crash with severe abrupt deceleration. The United States Federal Aviation Administration (FAA) has conducted extensive studies dealing with this special concern and has established a quantitative criterion for head injury probability: The head injury criterion (H.I.C.) is set forth as a numerical scale from zero to several thousand with a low number indicating a low probability of severe brain damage and a high number indicating a high probability of serious trauma or death. An event having a H.I.C. value below 1000 is considered to be one in which the probability of severe head injury is acceptably low; and such an event would be considered likely "survivable".
In a particular effort to improve airplane passenger safety and to set a standard considered reasonably achievable, the F.A.A. has mandated in Federal Aviation Regulation (F.A.R.) 25.562 that in a frontal crash in which the airframe undergoes up to a 16 g acceleration, the H.I.C. value for the passenger shall not exceed 1000.
Throughout the passenger seating space, the requirements of F.A.R. 25.562 are readily achievable by straightforward techniques of design and selection of materials with respect to the seating and other equipment and structure with, however, the exception of those seats immediately aft of bulkheads formed by cabin walls, lavatories, class dividers, galleys, or the like. In those seats, although some of the "deceleration" energy is absorbed by the airframe, the seat structure, and its attachment hardware, a passenger's head can be expected to impact the unaltered bulkhead catastrophically. The spacing of the seat backs to the bulkhead is typically about 35 inches; and the H.I.C. value could be made acceptable if the spacing of seat were increased enough to permit the passenger's body to pivot forwardly without head impact to the bulkhead. However, such a solution would require the loss of a row of seats at an effective airline revenue loss of approximately one million dollars per year per seat and would be a cost unacceptable to the passengers and the carrier in view of the extremely low probability of such an accident.
Another suggested solution is to provide mandatory shoulder harness restraints for those seats. Even if acceptable, this would require extensive structural engineering of seats with shoulder harness whose installation behind any bulkhead would reduce flexibility over conventional airplane seats, many of which in modern airplanes are otherwise convertible or moveable. In addition, shoulder harnessed seats cause passenger anxiety as to why some seats have a harness system while others do not.
Rear facing seats has been studied and rejected for many of the same reasons and, in addition, because any rear facing row would require radical modification to airplane interior arrangements.
In like manner, air bags have been extensively studied. This technology has many advantages and has been well developed for the automotive industry; however, the location and character of the crash sensor for a large, high velocity vehicle are unsolved difficult and critical problems. The sensor must reliably detect the initial crash or subsequent secondary impacts and deploy the airbag with extreme precision of timing. An inadvertent deployment could cause serious injury or death. The mechanism depends upon a seriously explosive event with the electrical ignition of powerful pyrotechnics; a situation undesirable in maintaining orderly evacuation from the aircraft. In addition, their maintenance and system reliability checks are complex and costly.
A further approach evidencing promise of providing a solution is an articulating, crash controlled seat pan for those particular bulkhead seats. Such a seat pan rotates and pitches upwardly by gravity and crash acceleration forces whereby the passenger's head is kept from striking the bulkhead. The seat system is complex and costly but can be engineered to fit within the existing seat envelope and provide acceptable H.I.C. values.
Another promising approach has been to develop energy absorbing pads or panels mounted on the bulkhead whereby a passenger's head strikes the pad and suffers an acceptable risk of serious injury. However, heretofore this approach has resulted in pads that 1) were too soft and in which the head would "bottom out" or would suffer such an uneven deceleration as to be ineffective, or 2) were too firm and caused the head to absorb a destructive amount of the kinetic energy, or 3) were too thick or heavy to be acceptable for use in the intended vehicle, or 4) were too elastic and caused dangerous recoil effects.
Accordingly it is an object of the present invention to provide an improved energy absorbing structure for ones body or a vulnerable portion thereof which structure does not suffer the limitations and disadvantages of this and other prior art and which assures H.I.C. values well below 1000 in a 16 g acceleration event.
It is another object to provide such structure which is reliable, durable, stable, low in maintenance or replacement cost, and which is rugged and relatively inexpensive to manufacture and install.
It is another object to provide such apparatus which is aesthetically unobtrusive and which is not susceptible to dents, scratches, or abrasions from exposure to casual events in its normal use environment.
It is another object to provide such structure which is light in weight.
It is another object to provide such apparatus which is totally passive in that it requires no electric or mechanical sensors, no actuators or other moving parts and is not susceptible to any inadvertent enablement or deployment.